Arfelli F, Assante M, Bonvicini V, Bravin A, Cantatore G, Castelli E, Dalla Palma L, Di Michiel M, Longo R, Olivo A, Pani S, Pontoni D, Poropat P, Prest M, Rashevsky A, Tromba G, Vacchi A, Vallazza E, Zanconati F
Sincrotrone Trieste SCpA, Italy.
Phys Med Biol. 1998 Oct;43(10):2845-52. doi: 10.1088/0031-9155/43/10/013.
Phase contrast x-ray imaging is a powerful technique for the detection of low-contrast details in weakly absorbing objects. This method is of possible relevance in the field of diagnostic radiology. In fact, imaging low-contrast details within soft tissue does not give satisfactory results in conventional x-ray absorption radiology, mammography being a typical example. Nevertheless, up to now all applications of the phase contrast technique, carried out on thin samples, have required radiation doses substantially higher than those delivered in conventional radiological examinations. To demonstrate the applicability of the method to mammography we produced phase contrast images of objects a few centimetres thick while delivering radiation doses lower than or comparable to doses needed in standard mammographic examinations (typically approximately 1 mGy mean glandular dose (MGD)). We show images of a custom mammographic phantom and of two specimens of human breast tissue obtained at the SYRMEP bending magnet beamline at Elettra, the Trieste synchrotron radiation facility. The introduction of an intensifier screen enabled us to obtain phase contrast images of these thick samples with radiation doses comparable to those used in mammography. Low absorbing details such as 50 microm thick nylon wires or thin calcium deposits (approximately 50 microm) within breast tissue, invisible with conventional techniques, are detected by means of the proposed method. We also find that the use of a bending magnet radiation source relaxes the previously reported requirements on source size for phase contrast imaging. Finally, the consistency of the results has been checked by theoretical simulations carried out for the purposes of this experiment.
相衬X射线成像技术是检测弱吸收物体中低对比度细节的有力手段。该方法在诊断放射学领域可能具有重要意义。事实上，在传统的X射线吸收放射学中，软组织内低对比度细节的成像效果并不理想，乳腺摄影就是一个典型例子。然而，到目前为止，在薄样品上进行的相衬技术的所有应用都需要比传统放射学检查高得多的辐射剂量。为了证明该方法在乳腺摄影中的适用性，我们在提供低于或相当于标准乳腺摄影检查所需剂量（通常平均腺体剂量约为1 mGy）的辐射剂量的同时，生成了几厘米厚物体的相衬图像。我们展示了在的里雅斯特同步辐射设施Elettra的SYRMEP弯铁光束线上获得的定制乳腺摄影体模和两个人类乳腺组织标本的图像。引入增感屏使我们能够以与乳腺摄影相当的辐射剂量获得这些厚样品的相衬图像。通过所提出的方法可以检测到传统技术无法看到的低吸收细节，如乳腺组织内50微米厚的尼龙线或薄钙沉积物（约50微米）。我们还发现，使用弯铁辐射源放宽了先前报道的相衬成像对源尺寸的要求。最后，通过为本实验目的进行的理论模拟检查了结果的一致性。
